A mobile telephone with an RFID tag reader and the use of such a telephone for localizing correspondingly tagged objects are well known. For example, WO 2006/092220 A2 describes a method for preventing the loss of keys that are coupled to an RFID tag. The mobile telephone determines and stores location information of the RFID tag and periodically evaluates an RFID signal received from the RFID tag to update the previously stored location information. If the user loses/misplaces his keys, he can review the stored location information and with the knowledge of the most recently known location the user has a good chance to retrieve the lost keys.